This is an accepted solution.
Nick here from Shopify.
If your free trial runs out and you haven't yet picked a plan, you wouldn't be able to access the back end/admin of the store. You would need to pick a plan in order to continue working on your store further. You will be prompted with a window to choose a plan after you log in. You can see more information about the free trial here and the plan prices here.
Let me know if you have any other questions about this or Shopify.
All the best, Nick
Thank you for your reply.
What if I pay for a payment plan but my store is not open yet? Am I able to freeze the payments on my plan until I start trading/open my store or not?
Anytime @jayboogie, glad it helped!
Once you select a plan the payments will begin. While you cannot work on your store and freeze the payments you can pause your store which means it wouldn't be open to the public but you could continue to work on it at a cheaper price.
"When you use the Pause and Build plan, your store continues to run at a reduced cost of $9 USD per month. You can access your Shopify admin and edit your products when you need to, but your checkout is disabled. This means that customers can see your products, but they can't purchase them."
You can see more about how to pause your store from the help guide Shopify has on this here. This would definitely be the cheapest and most effective way to work on your store until it is ready. Once you are ready to sell and open the checkout, you would need at least subscribe to the Shopify Basic plan.
Generally, your store information will remain intact for 30 days, possibly a short time longer.
This is great to know. I almost went with another provider because I have a lot of product to add to my store before I want to make it visible, like, months worth of work. I didn't like that shopify made you pay while you were building your site, but now that I see this (I have not seen this information anywhere else), it's a seal - the - deal for me. You should include this somewhere in your advertisement.